Odontologi - TP1MH1 Delkurs 1020 Sammanfattning av saliv

Sammanfattning av saliv – TP1MH1
Delkurs 1020 – Mikrobiologi, immunologi etc.

Oral Anatomy, Histology and Embryology, 4th edition
Berkovitz et al. , s. 260-272
ISBN: 9780723435518

Saliven – en nödvändighet för tandhälsan, Tandläkartidningen, nr 3, 1997
Lagerlöf et al.
Enligt gällande kursplan VT-13!

SALIVARY GLANDS

Compound – more than one tubule entering the main duct.
Tubuloacinar – morphology of the secreting cells.
Merocrine – only the secretion of the cell is released.
Exocrine – secretes fluid on to a free surface.
Secretion of saliva is a reflex function, dependent on afferent stimulation (such as taste).
99% water. Production of mucin. Lubricant during swallowing and speech.
Protects mucosa, keeps it moist.
Limits activity of bacteria by causing their aggregation.
Contains minerals – acts as a buffer.
Peptide growth factor produced by submandibular gland – involved in wound healing?
Immunoglobulin (IgA) - widespread mucosal immune system.
Amylase – aids digestion.
Two main elements:
- o Glandular secretory tissue – parenchyma.
- o Supporting connective tissue – stroma.
- o
- o
  Septa subdivide the gland into major lobes.
- o Lobes are divided into lobules.
  - § Each lobe contains grape-like structures – acini.
Acinus is serous, mucous or mixed.
Serous = more protein & less carbohydrate than mucous cells.
Secretion of saliva is under control of the ANS.
Acini of parenchyma responsible for primary secretion.
Major salivary glands: parotid, submandibular, sublingual.
Minor salivary glands: labial, buccal, palatoglossal, palatal, lingual.
Main regulated pathway – cells store and secrete protein by use of stored granule exocytosis.
- o Upon receipt of a neuronal signal.
- Second pathway – continuously by a vesicular mechanism.
  - o Constitutive pathway – some proteins may be secreted as they are synthesized.
  - SALIVARY GLYCOPROTEINS AND CALCIUM
    - o Salivary glands contain a mixture of neutral to acidic glycoproteins.
    - o Serous cells in parotid gland contain neutral glycoproteins.
    - o Mucous cells in submandibular, sublingual and minor glands contain acidic glycoproteins.
    - o Serous cells in submandibular gland contain a mixture of neutral & acidic.
    - o Intercalated duct cells often contain a mixture aswell.
    - o Striated duct cells often contain neutral glycoproteins.
    - o Ca2+ is incorporated in the secretory granule to neutralize the negatively charged parts of the glycoprotein.
      - § Prevents the glycoproteins from repelling each other.
      - § The more acidic glycoprotein à the more calcium is needed.

PAROTID GLAND

Largest of the salivary glands.
Serous saliva.
Granular appearance. Connective tissue contains blood vessels, nerves and collecting ducts.
Lumina of the acini are very narrow.
Intercalated ducts pass from acini and open into well represented striated ducts.
Ultrastructural appearance: cells have a wege-shaped outline.

Basal part delineated from surrounding connective tissue by a basal lamina.
Luminal part – dense, round secretory granules.
Narrow canaliculi run between the cells and join the lumen.
Adjacent cell membranes contact at desmosomes, gap junctions and tight junctions.
Secretory granules move towards luminal plasma membrane à become more electron-dense as protein content is concentrated.
Mitochondria provide energy for secretion of granules.
Following synthesis, resting (unstimulated) serous cells contain numerous secretory granules in cytoplasm.
Stimulated serous cells contain less secretory granules in cytoplasm. Discharged into the acinus lumini by exocytos.
Parasympathetic and sympathetic fibers act collaboratively in production of saliva during feeding.
Main neurotransmitter for:
- o Parasympathetic nerves – acetylcholine.
- o Sympathetic nerves – noradrenalin.
Each axon also contains arrays of neuropeptides.
Parasympathetic drive causes: formation and secretion of secretory granules.
Sympathetic drive causes: increases the output of preformed components from the cells.
Both pathways cause contraction of myoepithelial cells à helps direct fluid from acinar lumen out along the duct system.

Hypertonic = högre salthalt än serum.
Isotonic = samma salthalt som serum.
Hypotonic = mindre salthalt än serum.
Salivary glands secrete salt –Na and Cl - into the acinar lumina.
- o Hypertonic environment is created.
Channels in apical acinar cell membrane (toppen) are opened by signals from autonomic nerves .
- o Acetylcholine from parasympathetic nerves!
Cl streams into the acinar lumen.
Na moves into the acinar lumen to “utjämna” the difference.
Leads to movement of water into the lumen through aquaporin water channels!
Isotonic saliva in acina lumen is rendered hypotonic by removal of Na, Cl when passing through striated ducts.
Isoton saliv i acini – vid passage genom utförselgångarna reabsorberas ffa Na och Cl, vilket innebär att saliven är hypoton vid utsöndring.
- § Ju snabbare flöde, desto mindre reabsorption.
DUCT SYSTEM
Intercalated duct – the smallest.
- o Cubiodal epithelial tube.
- o Smooth on both luminal and basal surfaces.
- o Adjacent cells united with desomosomes.
- o Contribute to primary secretion.
- o Several acini drain into each intercalated duct.
Striated ducts – much longer and more active component in duct system than intercalated.
- o Luminal surface have short microvilli.
- o Basal (abluminal) surface have multiple striations – infoldings of the plasma membrane at the base of the cell.
  - § Mitochondria are packed between the infoldings.
  - § Adjacent cells anchored together by desmosomes.
  - o The created large surface is involved in active transport.
  - o Striations the site of electrolyte resorption (Na, Cl) and secretion (K) without loss of water.
  - o Resorption is against a concentration gradient à requires energy.
  - o Convert an isotonic or hypertonic fluid into a hypotonic fluid!
  - o Cells exhibit small secretory granules that may contain epidermal growthfactor, lysosome, IgA.
Collecting duct – main function is to transport saliva.
- o Compared to intercalated & striated ducts which also modify the composition of the saliva.
MYOEPITHELIAL CELLS
- o Around acini – dendritic cells. Outline of acinus remains smooth.
- o Around intercalated ducts – elongated. Outline produces a bulge.
- o Flattened nucleus, numerous contractile actin microfilaments.
- o Expresses CD44 when in contact with serous acinar cells.
  - § Therefore, may play a role in cell proliferation and differentiation.
  - o Myoepithelial activity can:
    - § Support the underlying parenchyma (secretory part) and reduce back-permeation of fluid.
    - § Accelerate the initial outflow of saliva.
    - § Reduce luminal volume (kontraktion?)
    - § Contribute to the secretory pressure.
    - § Milking effect on any underlying extracellular fluid.
BASAL CELLS
- o Present in striated (less) and collecting ducts (more).
- o Potential stem cells.
Lymph nodes are situated both on the surface and within the parotid gland.
- o Not found within the other salivary glands.

SUBMANDIBULAR GLAND

Second largest of the salivary glands. Mixed mucous/serous secretion.
The serous cells, duct system, myoepithelial cells and basal cells are the same as in parotid gland.
Shorter intercalated ducts, longer striated ducts.
MUCOUS CELLS
- o In the early stages of synthesis of its secretory products, much RER is present.
- o Have a more conspicuous Golgi apparatus compared to serous cells.
  - § Because of the greater amount of carbohydrate that is added to the secretory protein.
- o More pale secretory granules than serous cells.
- o Fewer microvilli and infoldings than that of a serous cell.
- o When filled with secretory granules, the nucleus is compressed against the basal surface.

SUBLINGUAL GLAND

Made up of a posterior part (greater sublingual gland) and an anterior part (lesser sublingual gland).
8-30 smaller salivary glands.
Mixed gland, but mostly mucous elements.
Serous cells in the gland might actually be immature mucous cells!
Secrete spontaneously and continuously.
DUCT SYSTEM
- o Much less developed compared to other major salivary glands.
- o Striated ducts are usually absent à saliva rich in K.

MINOR SALIVARY GLANDS

Buccal, labial, palatal, palatoglossal, lingual. 450-750.
Primarily mucous.
Have collecting ducts. Intercalated and striated ducts are genereally asbent.
Like sublingual gland, the duct system doesn’t remove as much salt, so the final saliva is isotonic and rich in K.
Parasympathetic nerve impulses.
Secrete spontaneously and continuously.

Saliven – en nödvändighet för tandhälsan
SEKRETION OCH SAMMANSÄTTNING

Sekretion aktiveras av parasympatiska (vatten och elektrolyter) och sympatiska (proteiner) nervsystemen som svar på olika stimuli.
Salivflödet påverkar koncentration av de flesta av salivens elektrolyter.
- o Klor, natrium och bikarbonat ökar med ökat flöde. Fosfat och magnesium minskar.
Dygnsrytmen spelar roll för koncentrationer av olika elektrolyter.
0,6 - 1 l saliv per dygn.
Vilosaliv påverkas av:
- o Dygnsrytmen – mindre under sömn. Mest på eftermiddagen.
- o Årstider – mindre på sommaren.
- o Kroppsställning – mindre i sittande, mer i liggande & stående.
- o Hälsotillstånd – Sjögrens syndrom minskar.
- o Farmaka - tex. antidepressiva med muntorrhet som biverkning.
- o Psykiska faktorer (ångest) påverkar flödet.
- o Kön, ålder, vikt etc. spelar mindre roll.
Stimulerad saliv påverkas av:
- o Samma som ovan.
- o Även smakstimuli – sura smaken salivstimulerande.
- o Mekanisk stimulering – tuggning.

SALIVENS FUNKTIONER

Mekaniskt skydd för tänder och slemhinnor.
- o Muciner (högmolekylära proteiner förenade med kolhydrater) smörjer.
- o Binder vatten – motverkar uttorkning av slemhinnorna.
Antimikrobiella egenskaper
- o Lysozym – bryter enzymatiskt upp vissa bakteriers skyddande hölje.
- o Laktoferrin – binder järn och minskar därmed tillgång av denna viktiga jon för bakterier.
- o Salivperoxidas katalyserar reaktionen mellan väteperoxid och tiocyanat à bildar toxisk substans för bakterier, hypotiocyanat.
- o Sekretoriska immunoglobuliner klumpar ihop bakterier till stora aggregat à sköljs bort.
- o Fluorjonen binder magnesium och hindrar därmed bakteriers ämnesomsättning (enzymet enolas kräver magnesium för glykolysen).
Reglering av munhålans pH-värde: 6,5-7,5.
- o Buffertsubstanser, såsom oorganiskt fosfat och bikarbonat, motverkar förändringar i pH.
- o Bikarbonat kan även tränga in i plack. Ju tjockare à ju svårare att verka i placket.
De- och remineralisation av tandvävnad
- o Upprätter jämvikten mellan tandsubstansens kalciumfosfater (hydroxylapatit) och omgivande vätskefas.
- o Intag av syror & minskat pH (erosion) eller syraproduktion i bakteriebeläggningar (karies) minskar möjlighet för remineralisation.
- o Vid remineralisation kan hydroxylapatitet även fällas ut i saliv (spottsten) och i bakteriebeläggningar (tandsten).
  - § Saliven innehåller utfällningshämmande ämnen för att hindra spottsten.
- o Fluorjon bromsar demineralisation och accelererar remineralisation.
- o

NEDDSATT SALIVKÖRTELFUNKTION

Kan orsaka kariesskador och skador på slemhinnor på lång sikt.
Symtom:
- o Torr munslemhinna med matt yta – munspegel fastnar då man stryker den mot slemhinnan.
- o Torra, spruckna läppar med fissurer på insidan (keilit).
- o Rodnad, blank tunga som ofta är fissurerad och/eller loberad.
- o Svampinfektioner (candida).
- o Svårigheter att tala.
- o Muntorrhet.
Salivflödesmätning.
- o Vilosaliv:
  - § Minst en timme utan intag av något slag.
  - § Vila 15 minuter före.
  - § Sitta i kuskställning, låt saliven passivt rinna över underläppen.
  - § Pågår i 15 minuter.
  - § Normalt viloflöde: 0,25-0,35 ml/min. Under 0,1 ml/min mycket lågt.
- o Stimulerad saliv:
  - § Kuskställning.
  - § Tugga på paraffinbit i 5 minuter. Töm saliv vid behov.
  - § Normalt flöde: 1-3 ml/min. Under 0,7 ml/min mycket lågt.
Behandlingsalternativ för muntorrhet:
- o Stimulera salivsekretion mha tuggummi och tabletter.
- o Sköljlösning och saliversättningsmedel.
- o Munvårdsprodukter som tillför salivens egna antimikrobiella komponenter (lysozym, laktoferrin etc).

KARIESFÖREBYGGANDE ÅTGÄRDER

Kariesutveckling kan bli ett problem på längre sikt.
Plackkontroll – instruktioner för rengöring av alla tandytor. Extra tandborstning före/efter måltid.
Kostråd – vätskerik och mild kost att föredra. Högst 4-5 måltider per dygn.
Fluortillförsel – fluortandkräm. Fluorskölj. Tuggummi / sugtablett.